19 Comments

Yosef Allam
on April 28, 2020 at 5:51 pm

Questions:
What is the mechanical force and type of equipment required, by your estimates, to be able to reliably raise and lower the ramp in an actual implementation given the mass of the full scale design?
What flow rates do some samples of the various elevations / angles correspond to? How do you know / how did you calculated this?
What functions do the boulders on the ramp in the water serve?
Will the flow rate-dependent angles serve all species of fish, or will the angles have to be periodically varied to serve different species per given set of conditions?

As testing was limited, we did not calculate the exact flows associated with different angles. We used the lowest estimate for rock ramp design specified by the United States Forest Service to be the maximum slope.

The boulders serve to slow the flow of the water. Larger boulders are placed to create a small hydraulic back-flow, this allows water to pool at measured points on the ramp. The pools allow fish to rest as they ascend the ramp. Smaller rocks serve to create ripples, which slow water at it flows through the ramp.

We have data on which species live on the South Platte River at River Run Park. We used the data from the United States Forest Service to judge which standards to implement into the whitewater park. We have the ability to lower the ramp as needed to accommodate a variety of swimming abilities.

Fish follow the flow of downstream current. While they may attempt to pass through the whitewater park, the fish that cannot swim through the whitewater park will eventually sense the current from the rock ramp.

To respond to the first part of your question,
Given the mass of the full scale design, which is an estimated 8,000lbs (including the addition of the upper bounds of the weight of water that will be flowing across the ramp), 159,889.32 ft.lbs would be required to reliably adjust the ramp’s position. With this in mind, a motor with 50Hp and an RPM of 885, multiplied by the gear ratio of 625:1 provided by the gear assembly, will provide 185,452 ft.lbs, which will be sufficient in being able to change the ramp’s position, even with the addition of extra unplanned weight.

Hi Team!
Nice work! To what degree might diverting water over the ramp affect the flow over the white water feature installed? Meaning, what percentage of the river flow will be diverted, and what does this mean?
Thank you, Leslie

The rock ramp is 4ft wide and about 1.5ft deep, so the volume of water required is quite small compared tot he river channel. The back-flow pools allow the ramp to retain water, leaving enough water for fish to swim through the ramp. Therefore the percentage of river flow needed to operate the rock ramp is quite low and will allow the whitewater park to function properly.

After watching the video, I’m intrigued by the concept and have some follow-up questions:
1) Maintenance: initial costs are low ($13K), but what are anticipated maintenance costs over time? Can it be serviced in the water, or must it be removed for maintenance?

2) Potential impacts of flooding: how resilient is your design (the ramp itself, the installation infrastructure, and the large boulders at the inflow/outflow) to flooding? What maximum levels of flows did you consider (e.g., 5-year, 50-year, or 100-year flows)?

3) Acceptance: Did you talk to boaters and/or whitewater outfitters about their willingness to see it in use? If so, what was their feedback? Will recreationists accept having such a feature installed in whitewater parks?

4) Inflow/outflow: Will the large boulders meant to dissuade boaters potentially dissuade fish from using it? Given that the boulders will change flow patterns, and that boulders could potentially be dislodged by flood flows, did you consider alternative ways of marking the inflow/outflow to keep boaters away?

For maintenance we chose the electronic components based on durability. They are all well tested and have great warranties.We have implemented an access panel that will allow for relatively easy maintenance to be done if gears happen to break or if electronic components go down. In order to put the least amount of strain on our motor, we have chosen to run it on 460VAC which will give it a service factor of 1.15, allowing for overwork if necessary. Other than the motor, the only parts that may need replacement are the gears or sensors. The gears are priced in total at $850 so if any of them need to be replaced it won’t cost much. They are designed to handle the system they are being placed in so we don’t expect much wear. The depth sensor will probably be the most quickly degrading component in the system, but at a cost of only $341 it is a relatively pain free fix.

When modeling our system, we used 3000 cubic feet per second (cfs) to be the maximum flow based on 15 years of flow data. Such flows were used to estimate the specification of ramp flow required for fish passage. A flooding event may very well remove boulders from the ramp or dislodge the large boulders used to guard the entrance and exit of the ramp. However, they will all be cemented in place which will help to deter this from happening. Even though the ramp may be impacted, the overall system will not be dislodged. Any rocks or boulders that get washed away or displaced can be easily repaired or replaced at a low cost.

The adjustable rock ramp will not impact recreational use. After speaking to boaters, their primary concern is accessibility to the wave feature. In order to access the wave, boaters often have to go through rapid water to reach the standing wave. With the safety bridge implemented, they will have easier access to the standing wave. They will actually be benefitted by this fish passage feature.
The standing wave is the feature that creates the recreational attraction. When flow depths are low, the boaters don’t use the WWP. Thus, when the rock ramp is adjusted to accommodate the low flow without impacting the boaters. When there is high flow and the boaters are using the WWP, the ramp will be raised. Although the rock ramp will take away a small amount of water from the standing wave, it will be insignificant in comparison to the size of the channel which typically range from 20-30 feet.

There are wide enough gaps between the boulders to allow fish to sense the flow without them getting dissuaded from use. Additionally, these gaps are wide enough to not severely impact the flow. We did consider other methods, such as warning signs telling people to stay away, but that wouldn’t solve the problem of people being accidentally swept towards the ladder. The boulders themselves would be cemented and bolted down to minimize any chance of them dislodging.

Thank you for that comprehensive answer. Last question – did the issue of permitting ever come up? In-stream work (initial installation and any ongoing replacement of boulders, etc.) would typically require one or more permits. Such work would likely be covered by whatever permit(s) a whitewater park obtained for the park itself, but I’m curious if anyone mentioned permits to you.

There are numerous requirements that whitewater parks must meet in order to receive permitting. For instance, water quality, fish, wildlife, and habitat standards must be met. The rock ramp would have to meet the same requirements. The ramp’s safety considerations cover both humans and animals. While there may be some specifications that change during the permitting process, we are confident that our ramp will be able to pass permitting requirements. We do find it interesting that this is the first time we heard about permitting throughout this project, as none of the engineers or stakeholders interviewed mentioned it. We did find all the specific rules and regulations required for building any type of dam in a Colorado river, however, these regulations will differ depending on the state requirements and regulations.

Grace – thanks for this information. Indeed, permitting is critical to consider from the beginning of projects, especially those that have any impact or nexus to water – wetlands, streams, rivers, lakes, etc. In Colorado, in-stream projects have significant permitting requirements – which can require months of time, and thousands of dollars to acquire.

Ryan Meyer
on April 29, 2020 at 10:25 am

Great work team.

1. I’m wondering if there might be a more economical way to get the ramp to move. Were other alternatives looked at in lieu of the motor? A 50 HP motor is not small, and may require new and additional electrical infrastructure to these rather remote sites. How about an air bladder?

Although we originally considered an air bladder, we eventually chose to use a motor and gear system for more precise adjustments. Since the fish require a specific flow rate to travel upstream, we determined a motor and gear system would best fulfill our specifications. In our research we also found that moisture and high temperature changes can be very detrimental to air compressors. As this application sits directly in water, it limits the use of both air bladders and pneumatic pistons. A major issue when considering the use of a hydraulic piston, is that while the risk of a leak is low, the fluid used by these pistons is very harmful to the environment.

Since there are several large buildings in the near vicinity of River Run park, hooking the system to the main power grid should not be a problem. We have addressed the issue of having high voltage in and around the river, and have found solutions which mitigate this entirely. The breaker box will be located on the bank above the flood levels, and all of the wiring will be encased in waterproof conduit. Many of these WWP’s are located in remote areas, and in these situations we would certainly be required to readdress the power issues.

Interesting idea that has a lot of potential. I’m wondering want other options besides motorized and air bladder operation you might have considered in your idea generation. Also, did you have a chance to speak with the designers/contractors responsible for designing and building white water parks to get their opinion? Finally, did you consider implementing this design in existing parks, or only new construction?

When we first started generating ideas, we thought about making a floating rock ramp. By using flotation devices similar to docks, we could calculate the amount of pressure needed to keep the ramp underwater and allow the desired flow to run over the ramp. Although this solution may be effective in some situations, we determined that any feature that is implemented into WWP’s must be sturdy enough to withstand the hydraulic forces. Additionally, because of the rapid waters that these channels create, a floatation device wouldn’t be durable or safe enough to withstand these waters.

In speaking with the company responsible for building River Run park, their main concern was making sure that the rock ramp was relatively cheap compared to the overall cost of the WWP. They liked the idea of the rock ramp, but did not want to add too much to the significant cost of the WWP.

As far as implementing this design, it makes the most sense based on our research to only place it in new projects. These will already have acquired the necessary permits and usually have budgets upwards of $500K. If we were to try and retrofit an existing WWP with this design, it would require an extensive redirection of the river which would close the WWP, as well as demolition of part of the existing structure. Although this is possible, it would significantly increase the cost as we would now be required to obtain permits for this specific construction. These can be difficult and costly to obtain and require a lengthy waiting period.

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